1. Field of the Invention
The invention relates to processes which entail an exothermic reaction of a fluid process stream, and is especially applicable to exothermic catalytic reactions such as the oxidation of sulfur dioxide to sulfur trioxide, ammonia or methanol synthesis, or the catalytic elimination of residual nitrogen oxides from the tail gas discharged from nitric acid production by reaction of the nitrogen oxides with a reducing gas such as methane or hydrogen. In these various and similar reactions, the cold feed gas must be heated to a suitable ignition temperature to initiate the reaction, and excessively high reaction temperatures must be avoided.
2. Description of the Prior Art
The use of ejectors or aspirators for recycling and mixing in various processes is described in Gillespie, G. R. et al "Catalytic Purification of Nitric Acid Tail Gas" AIChE Meeting (Dec. 2, 1971) page 8 and FIG. 7 and in Kirk-Othmer "Encyclopedia of Chemical Technology" Interscience-Wiley (1964) Edition-2, Volume-4, pages 410-412 and in Foster Wheeler Corp. Bulletin 0-54-1 (1954) pages 8 and 9. The general prior art practice with respect to ejectors or aspirators for recycling and mixing in conjunction with exothermic reactions has been to pass the effluent stream from the immediate reaction zone to a zone or zones where cooling at least in part is effected either purposefully and desirably as in cases to obtain product condensation and removal as in the Foster Wheeler reference, or again purposefully and desirably as in cases to obtain process requisite heat transfer as in the Kirk-Othmer reference, or involuntarily and undesirably as in cases of thermal losses to ambient as resulting from the Gillespie et al method of application. All of the referenced prior art practices are accompanied furthermore by relatively long flow path and significant pressure loss.
The use of fans or blowers for recycling and mixing in various processes is described in Nonhebel, G. "Gas Purification Processes," George Newnes Ltd. (1964) pages 432, 450, 451 and in Kohl & Riesenfeld "Gas Purification," McGraw Hill Inc. (1960) pages 473 and 479. The general prior art practice with respect to fans or blowers for recycling and mixing in conjunction with exothermic reactions has been limited in application according to temperature and pressure restrictions for the fans or blowers and to the unavoidably cumbersome nature of such installations.
Apparatus for exothermic catalytic reactions is described in U.S. Pat. Nos. 3,498,752; 3,475,137; 3,443,910; 3,433,600; 3,366,461; 3,366,460; 3,212,862 and 3,041,151. Processes for elimination of nitrogen oxides from nitric acid plant tail gas are described in U.S. Pat. Nos. 3,565,575; 3,467,492; 2,970,034 and 3,443,910. Improvements in catalytic methanol synthesis are disclosed in U.S. Pat. Nos. 3,597,465; 3,531,266 and 3,186,145, and improvements in catalytic ammonia synthesis are described in U.S. Pat. Nos. 3,349,569 and 3,232,707.
Sulfuric acid process improvements are described in U.S. Pat. Nos. 3,653,828; 3,536,446; 3,519,388; 3,475,120; 3,455,652; 3,434,263; 3,350,169; 3,172,725 and 3,147,074. Nitric acid production or analogous processing is described in U.S. Pat. Nos. 3,542,510; 3,499,734 and 3,102,788.